/*
 * PullProvider.java January 2010
 *
 * Copyright (C) 2010, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.stream;

import java.io.InputStream;
import java.io.Reader;

import wx.xml.xmlpull.v1.XmlPullParser;
import wx.xml.xmlpull.v1.XmlPullParserFactory;

/**
 * The <code>PullProvider</code> class is used to provide an event
 * reader that uses the XML pull API available on Google Android. It
 * provides the best performance on Android as it avoids having to
 * build a full DOM model. The <code>EventReader</code> produced by
 * this provider will have full namespace capabilities and also has
 * line numbers available for each of the events that are extracted.
 *
 * @author Niall Gallagher
 */
class PullProvider implements Provider {

    /**
     * This is used to create a new XML pull parser for the reader.
     */
    private final XmlPullParserFactory factory;

    /**
     * Constructor for the <code>PullProvider</code> object. This
     * will instantiate a namespace aware pull parser factory that
     * will be used to parse the XML documents that are read by
     * the framework. If XML pull is not available this will fail.
     */
    public PullProvider() throws Exception {
        this.factory = XmlPullParserFactory.newInstance();
        this.factory.setNamespaceAware(true);
    }

    /**
     * This provides an <code>EventReader</code> that will read from
     * the specified input stream. When reading from an input stream
     * the character encoding should be taken from the XML prolog or
     * it should default to the UTF-8 character encoding.
     *
     * @param source this is the stream to read the document with
     * @return this is used to return the event reader implementation
     */
    public EventReader provide(InputStream source) throws Exception {
        XmlPullParser parser = factory.newPullParser();

        if (source != null) {
            parser.setInput(source, null);
        }
        return new PullReader(parser);
    }

    /**
     * This provides an <code>EventReader</code> that will read from
     * the specified reader. When reading from a reader the character
     * encoding should be the same as the source XML document.
     *
     * @param source this is the reader to read the document with
     * @return this is used to return the event reader implementation
     */
    public EventReader provide(Reader source) throws Exception {
        XmlPullParser parser = factory.newPullParser();

        if (source != null) {
            parser.setInput(source);
        }
        return new PullReader(parser);
    }
}
